Auxin fluxes in the root apex co-regulate gravitropism and lateral root initiation

International audienceRoot architecture plays an important role in water and nutrient acquisition and in the ability of the plant to adapt to the soil. Lateral root development is the main determinant of the shape of the root system and is controlled by external factors such as nutrient concentration. Here it is shown that lateral root initiation and root gravitropism, two processes that are regulated by auxin, are co-regulated in Arabidopsis. A mathematical model was generated that can predict the effects of gravistimulations on lateral root initiation density and suggests that lateral root initiation is controlled by an inhibitory fields mechanism. Moreover, gene transactivation experiments suggest a mechanism involving a single auxin transport route for both responses. Finally, co-regulation may offer a selective advantage by optimizing soil exploration as supported by a simple quantitative analysis

Modeling auxin fluxes and Arabidopsis root ramification at different scales

International audienceno abstrac

Photoswitchable single-walled carbon nanotubes for super-resolution microscopy in the near-infrared

The design of single-molecule photoswitchable emitters was the first milestone toward the advent of single-molecule localization microscopy, setting a new paradigm in the field of optical imaging. Several photoswitchable emitters have been developed, but they all fluoresce in the visible or far-red ranges, missing the desirable near-infrared window where biological tissues are most transparent. Moreover, photocontrol of individual emitters in the near-infrared would be highly desirable for elementary optical molecular switches or information storage elements since most communication data transfer protocols are established in this spectral range. Here, we introduce a type of hybrid nanomaterials consisting of single-wall carbon nanotubes covalently functionalized with photoswitching molecules that are used to control the intrinsic luminescence of the single nanotubes in the near-infrared (beyond 1 μm). Through the control of photoswitching, we demonstrate super-localization imaging of nanotubes unresolved by diffraction-limited microscopy

Active strike-slip faults and an outer frontal thrust in the Himalayan foreland basin

The Himalayan mountain belt results from continuing convergence between the Indian Plate and Asia. Damaging earthquakes occur on major thrust faults north of the Main Frontal Thrust (MFT). To the south, the Ganga foreland basin is typically described as undeformed. We show that active thrust and strike-slip faults, with accumulated slip up to ∼100 m, pass under the trace of the MFT into the foreland basin in eastern Nepal, leading to propagation of deformation at least ∼37 km into the foreland basin beneath the densely populated Ganga plain. The development of these faults at the active thrust front helps to explain structures preserved in higher thrust sheets of the Himalaya, and in ancient mountain belts elsewhere

Auscultation des assemblages collés par acousto-ultrasons : Application à des assemblages acier-composite du génie civil

JNC 21, Journées Nationales sur les Composites, BORDEAUX, FRANCE, 01-/07/2019 - 03/07/2019Le renforcement des structures (béton et acier) par collage de matériau composite est de plus en plus fréquent dans le domaine du génie civil depuis les années 80-90. Cependant, des défauts et/ou endommagements présents dans l'assemblage collé diminuent l'efficacité de cette solution technique. Dès lors, il est nécessaire de mettre à la disposition de ses futurs utilisateurs des outils pour détecter, voir identifier des défauts et/ou endommagements présents dans ces assemblages collés sans pour autant nuire à leur future utilisation.Les techniques actuellement utilisées dans l'auscultation des assemblages collés ne permettent pas détecter des zones mal polymérisées ou des défauts d'adhésion. La détection de ces types de défaut constitue donc un verrou important freinant l'utilisation du collage structural. Dans cette étude, nous éprouvons la potentialité de la technique des acousto-ultrasons à répondre à cette problématique.Une série d'assemblages collés de renforts composites sur plaque métallique a été réalisée avec différents types de défauts maitrisés. Des mesures par acousto-ultrasons ont permis d'évaluer dans un premier temps la répétabilité de la technique puis d'estimer sa capacité à détecter et discerner les défauts étudiés. Plusieurs méthodologies ont été évaluées : une analyse des coefficients de corrélation des spectres fréquentiels, une analyse paramétrique et enfin une Analyse par Composantes Principales (ACP).L'analyse paramétrique s'est avérée efficace à déceler les défauts d'adhésion et de vieillissement de la colle. Une exploitation des données de type Analyse par Composantes Principales a été nécessaire afin de pouvoir détecter l'ensemble des défauts étudiés

Spatial Intensity Distribution Analysis Reveals Abnormal Oligomerization of Proteins in Single Cells

AbstractKnowledge of membrane receptor organization is essential for understanding the initial steps in cell signaling and trafficking mechanisms, but quantitative analysis of receptor interactions at the single-cell level and in different cellular compartments has remained highly challenging. To achieve this, we apply a quantitative image analysis technique—spatial intensity distribution analysis (SpIDA)—that can measure fluorescent particle concentrations and oligomerization states within different subcellular compartments in live cells. An important technical challenge faced by fluorescence microscopy-based measurement of oligomerization is the fidelity of receptor labeling. In practice, imperfect labeling biases the distribution of oligomeric states measured within an aggregated system. We extend SpIDA to enable analysis of high-order oligomers from fluorescence microscopy images, by including a probability weighted correction algorithm for nonemitting labels. We demonstrated that this fraction of nonemitting probes could be estimated in single cells using SpIDA measurements on model systems with known oligomerization state. Previously, this artifact was measured using single-step photobleaching. This approach was validated using computer-simulated data and the imperfect labeling was quantified in cells with ion channels of known oligomer subunit count. It was then applied to quantify the oligomerization states in different cell compartments of the proteolipid protein (PLP) expressed in COS-7 cells. Expression of a mutant PLP linked to impaired trafficking resulted in the detection of PLP tetramers that persist in the endoplasmic reticulum, while no difference was measured at the membrane between the distributions of wild-type and mutated PLPs. Our results demonstrate that SpIDA allows measurement of protein oligomerization in different compartments of intact cells, even when fractional mislabeling occurs as well as photobleaching during the imaging process, and reveals insights into the mechanism underlying impaired trafficking of PLP